Solar Energy Substrate Aerodynamic Flaps

ABSTRACT

Methods and systems for solar energy capture. One of the systems includes a solar energy substrate mounted on a support member and one or more flap assemblies coupled to the solar energy substrate. The solar energy substrate is configured to receive solar rays from the Sun and is further configured to move in at least one direction such that an orientation of the solar energy substrate can be adjusted in accordance with a direction of the solar rays. The support member is configured to support the solar energy substrate. The one or more flap assemblies each include a flap and an actuator that is configured to move the flap relative to the solar energy substrate. Movement of the flap is controllable to counter a wind-induced moment acting on the solar energy substrate.

TECHNICAL FIELD

This specification relates to aerodynamic flaps for use with solar energy substrates.

BACKGROUND

A solar energy substrate can be a substrate that is generally directed toward the Sun and moves in at least one direction to track the Sun as the Sun appears to move across the sky. A mirror (or collection of mirrors) included in a heliostat is an example of a solar energy substrate. The mirror reflects solar rays that are incident on the mirror toward a receiver that is typically mounted on a receiver tower. Solar rays that are directed to the receiver can be used to generate electricity. A field of heliostats can be placed surrounding one or more receivers to increase the quantity of radiation collected and optimize the amount of electricity that is generated. A photovoltaic panel that includes one or more photovoltaic cells is another example of a solar energy substrate. The photovoltaic panel tracks the Sun to optimize solar energy absorption. Solar energy substrates are typically mounted onto a structure such as a pole and placed in a field to receive sunlight free from obstructions. The solar energy substrates are subjected to environmental conditions including wind, which can have a tendency to affect the orientation of the solar energy substrate, which may negatively impact the efficiency of the solar energy substrate in receiving solar rays.

SUMMARY

In general, one aspect, the subject matter described in this specification can be embodied in a solar energy system that includes a solar energy substrate mounted on a support member and one or more flap assemblies coupled to the solar energy substrate. The solar energy substrate is configured to receive solar rays from the Sun and is further configured to move in at least one direction such that an orientation of the solar energy substrate can be adjusted in accordance with a direction of the solar rays. The support member is configured to support the solar energy substrate. The one or more flap assemblies each include a flap and an actuator that is configured to move the flap relative to the solar energy substrate. Movement of the flap is controllable to counter a wind-induced moment acting on the solar energy substrate. Other embodiments of this aspect include corresponding methods.

These and other embodiments can each optionally include one or more of the following features, alone or in combination. The solar energy system can further includes a control system that is configured to receive information that indicates the wind-induced moment is acting on the solar energy substrate; and to control movement of the one or more flaps to reduce the wind-induced moment. The solar energy substrate can be a heliostat mirror configured to reflect the received solar rays toward a solar energy collector or can be a photovoltaic panel. The solar energy substrate can be a unitary member or include two or more members. If there are two or more members, orientations of the two or more members can be independently adjustable.

The flaps of the one or more flap assemblies can be connected to one or more edge regions of the solar energy substrate. Each flap can be connected to an edge region of the solar energy substrate and can be positioned at an angle relative to a first plane that is different than an angle of the solar energy member relative to the first plane. The angle of the flap relative to the first plane can be determined based on a strength of the wind-induced moment acting on the solar energy substrate. Each flap can be connected to the edge region with a hinge that provides pivotal movement of the flap relative to the solar energy substrate. Each actuator can be a linear actuator coupled at a first end to the solar energy member and at a second end to the flap and can be configured to change the angle of the flap relative to the first plane.

In general, in another aspect, the subject matter described in this specification can be embodied in methods that include: (a) detecting that a wind-induced moment is acting on a solar energy substrate mounted to a support structure, wherein the solar energy substrate is positioned at a particular time in a desired position relative to a position of the Sun at the particular time and in the desired position the solar energy substrate is at an angle α relative to a first plane; (b) in response to detecting the wind-induced moment, adjusting a position of a flap coupled to an edge region of the solar energy substrate including adjusting an angle Θ of the flap relative to the first plane, wherein the angle Θ is different than the angle α; and (c) repeating steps (a) and (b) until the detected wind-induced moment is reduced to a strength that is less than or equal to a predetermined threshold value.

These and other embodiments can each optionally include one or more of the following features, alone or in combination. Detecting that a wind-induced moment is acting on the solar energy substrate can include detecting at least one of voltage or current in one or more motors configured to adjust a position of the solar energy substrate and operating at the particular time to counter the wind-induced moment and maintain the solar energy substrate in the desired position. Detecting that a wind-induced moment is acting on the solar energy substrate can include detecting tension exceeding a threshold value in one or more cables configured to adjust a position of the solar energy substrate and operating at the particular time to counter the wind-induced moment and maintain the solar energy substrate in the desired position. Adjusting the position of the flap can include operating a linear actuator to extend or retract a linear member that is coupled to the flap at a first end and to the solar energy substrate at a second end to adjust the angle Θ of the flap relative to the first plane.

In general, in another aspect, the subject matter described in this specification can be embodied in a solar energy system that includes a solar energy substrate mounted on a support member and configured to receive solar rays from the Sun and configured to move in at least one direction such that an orientation of the solar energy substrate can be adjusted in accordance with a direction of the solar rays. The system further includes the support member, which is configured to support the solar energy substrate. The system further includes one or more flap assemblies coupled to the solar energy substrate. Each flap assembly includes a flap and an actuator that is configured to move the flap relative to the solar energy substrate and movement of the flap is controllable to control movement of the solar energy substrate.

These and other embodiments can each optionally include one or more of the following features, alone or in combination. The solar energy system can further include a control system that is configured to receive information that indicates that the solar energy substrate is oscillating; and control movement of the one or more flaps to reduce oscillation of the solar energy substrate.

In some implementations, the control system is configured to receive information that indicates that a wind-induced moment is acting on the solar energy substrate; and control movement of the one or more flaps to reduce the wind-induced moment. In some implementations, the control system is configured to receive information that indicates that a wind load is acting on the solar energy substrate, and control movement of the one or more flaps to adjust a position of the solar energy substrate using the wind load.

Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. Maintaining a desired orientation of a solar energy substrate, e.g., a heliostat mirror or a photovoltaic panel, included in a solar energy system is important for the solar energy substrate to operate effectively. A drive system that operates to position the solar energy substrate may also operate to counter a wind load on the solar energy substrate that is inducing a moment, otherwise the solar energy substrate will be blown off position (i.e., moved so as to point off-target). The harder the drive system has to work to counter a wind-induced moment, the more energy the overall solar energy system consumes, for example, on account of electricity used by one or more motors included in the drive system. Including one or more flap assemblies coupled to the solar energy substrate allows the aerodynamics of the solar energy substrate to be adjusted dynamically based on a current wind load acting on the substrate. One or more flaps included in the one or more flap assemblies can be positioned to counter a wind-induced moment and to reduce the moment to zero or near-zero. Reducing or eliminating the moment results in less work required by the drive system to maintain the solar energy substrate in the desired position, and improved system efficiency.

The one or more flap assemblies can be configured and operated to reduce oscillation of the solar energy substrate. Although the flap assemblies can be used to reduce the load on the drive system, e.g., on a motor or motors, to zero, in a zero load position oscillation of the solar energy substrate may actually increase. The one or more flap assemblies can be position to produce a slight bias to one side of zero, thereby reducing the oscillation range. In some implementations, the flap assemblies can be positioned and operated to use wind loads to assist in moving the solar energy substrate to another position.

The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example conventional heliostat.

FIG. 2 shows a schematic representation of a side view of an example solar energy system including a solar energy substrate subjected to a wind load.

FIG. 3 shows a schematic representation of a side view of an example solar energy system including a solar energy substrate and flap assembly subjected to a wind load.

FIG. 4 is a schematic representation of forces and moments acting on the example solar energy system of FIG. 3.

FIG. 5 is a schematic representation of an example solar energy system including two flap assemblies.

FIG. 6 is a schematic representation of a front view of an example solar energy system with multiple flap assemblies.

FIGS. 7A, 7B and 7C are schematic representations of an example solar energy system with a retractable flap assembly.

FIG. 8 is a flowchart showing an example process for controlling the orientation of a solar energy substrate.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

A solar energy system includes a solar energy substrate mounted on a support member where the solar energy substrate is configured to receive solar rays from the Sun. The solar energy substrate is configured to move in at least one direction such that an orientation of the solar energy substrate can be adjusted in accordance with a current position of the Sun. For example, if the solar energy system is a heliostat, the solar energy substrate is one or more mirrors that are oriented to receive the solar rays and to reflect them toward a solar energy collector (e.g., a receiver). As the direction of the incoming solar rays changes with the movement of the Sun relative to the heliostat, the solar energy substrate is re-oriented (e.g., in elevation and/or azimuth) to most effectively receive and reflect the solar rays. In another example, the solar energy substrate is a photovoltaic panel that includes one more photovoltaic cells. The orientation of the panel can be adjusted (e.g., in elevation and/or azimuth) to track the relative position of the Sun to maximize solar energy absorption by the panel. The solar energy system further includes the support member, which is configured to support the solar energy substrate. The support member can be constructed in various configurations including, for example, as a pole or a framed tower.

One or more flap assemblies are coupled to the solar energy substrate. It should be understood that a flap assembly that is coupled to the solar energy substrate can be coupled either directly or indirectly. For example, the flap assembly can be connected directly to the solar energy substrate, e.g., to an edge, edge region or elsewhere. In another example, the flap assembly can be connected to a framework that supports the solar energy substrate, and thereby indirectly coupled to the solar energy substrate.

Each flap assembly includes a flap and an actuator that is configured to move the flap relative to the solar energy substrate. Movement of the flap is controllable to counter a wind-induced moment acting on the solar energy substrate. The flap effectively changes the aerodynamic properties of the solar energy substrate. Because the flap can be moved, the aerodynamics of the solar energy substrate is adjustable. If wind is inducing a torque (moment) on the solar energy substrate, the aerodynamics can be adjusted to counter the moment and stabilize the substrate while subjected to the wind load. Wind is typically not constant and changes over time. The flap can thereby be dynamically moved in approximately real-time in response to a changing moment acting on the substrate due to a changing wind load. It should be understood that there are other moments that can be acting on the solar energy substrate that can change, e.g., a gravity-induced moment that can change as an unbalanced system rotates, and as long as there is a wind blowing to gain work from, the one or more flaps can attempt to counteract them.

FIG. 1 shows an example conventional heliostat 100. The heliostat 100 includes a solar energy substrate 102, which in this example is a faceted mirror formed from multiple mirror panels (collectively referred to as the solar energy substrate). A rack assembly 104 mounts the solar energy substrate 102 on the support member 112 which is secured to a foundation 116. An azimuth and elevation drive mechanism 106 is included to adjust the azimuth and elevation of the solar energy substrate 102. The heliostat 100 further includes an encoder 108, electronics 110 and a power box 114. A wind load 101 directed toward the face of the solar energy substrate 102, i.e., coming from the left of the figure directed toward the right, would induce a moment on the solar energy substrate that would tend to urge the substrate into a substantially vertical position. However, if the desired position of the substrate is not substantially vertical, i.e., in order to effectively receive and reflect solar rays, then the drive mechanism 106 must work against the wind load to hold the substrate in the desired position.

FIG. 2 shows a schematic representation of a side view of an example solar energy system 200 including a solar energy substrate 204 subjected to loads from wind 216 (referred to hereafter as the “wind load 216”). The effect of a wind load on a conventional heliostat (e.g., heliostat 100) or other type of solar energy system 200 can be described with reference to this figure. The forces and moments on the solar energy substrate 204 can be forces in the three directions of x, y and z (shown with reference to the coordinate system 208) and moments about those same directions. The forces on the solar energy substrate 204 are typically drag forces, acting generally in the direction of the wind 216, upward forces acting generally in the z-direction and a rotational moment that tries to rotate the angled substrate 204, which is supported at a fixed point, i.e., point 206.

The forces and moments are described in reference to a three-dimensional coordinate system 208 having an x-axis 210 that extends from left to right, a z-axis 214 that extends from the bottom of the figure to the top and a y-axis 212 that extends into and out of the page. The wind 216 in the example shown is in the x direction and generates a force F_(x) 218 and a force F_(z) on the solar energy substrate 204, which is shown angled and is supported by a support member 202. For purposes of this example, it is assumed that the angled position of the solar energy substrate 204 is the desired position for receiving solar rays from the Sun at a particular time. A wind-induced moment M_(y) 222 about the y-axis is also generated by the wind load 216. The moment is drawn in the direction that the wind would impose on the substrate 204 presented to the wind at the angle shown. This is a negative moment with the coordinate system 208 as drawn. The wind tries to rotate the flat solar energy substrate 204 so that it is normal to the wind. The support member 202 and a drive mechanism for the heliostat 200, that operates to change the orientation of the substrate 204 (i.e., in azimuth and elevation), act against the forces and moments, e.g., forces F_(x), F_(z) and the moment M_(y), to counteract the wind load 216 and maintain the substrate 204 in the desired orientation; the support member 202 resists the forces and moment and the drive mechanism also operates to resist the moment.

FIG. 3 shows a schematic representation of a side view of an example solar energy system 300 including a solar energy substrate 304 and flap assembly 305 subjected to a wind load 316. The flap assembly 305 includes a flap 307 that is coupled to the solar energy substrate 304 by a connector 309. In the particular example shown, the connector 309 is a hinged connector allowing pivotal movement of the flap 307 relative to the substrate 304. The flap assembly 305 further includes an actuator mechanism 303. In this example, the actuator mechanism 303 is implemented as a linear actuator, although other configurations of actuator can be used. The solar energy substrate (e.g., heliostat mirror or photovoltaic panel) is mounted on a support member 302 and is rotateably movable in elevation and azimuth about the point 306 by a drive mechanism. The solar energy system 300 shown is simplified in terms of the elevation and azimuth drive mechanism and the mounting structure, however, it should be understood that an azimuth and elevation drive mechanism is configured to adjust the azimuth and elevation of the solar energy substrate 304 (e.g., with one or more motors).

The solar energy substrate 304 is shown tilted at an angle α relative to a substantially horizontal plane, i.e., a plane parallel with the x-axis. The flap 307 is shown tilted at an angle Θ relative to the horizontal plane. The angle Θ is different than the angle α; the flap can be oriented independently (at least with respect to angle Θ) from the orientation of the substrate 304. That is, the actuator mechanism 303 is used to adjust the angle Θ of the flap 307.

FIG. 4 is a schematic representation of forces and moments acting on the example solar energy system of FIG. 3. That is, the wind load 316 applies a force F_(x) 318 in the x-direction and a force F_(z) 320 in the z-direction and induces a moment M_(y) 322 about the y-axis on the solar energy substrate 304. Additionally, the wind load 316 applies a force F_(x2) 324 in the x-direction and a force F_(z2) 326 in the z-direction and induces a moment M_(y2) 328 about the y-axis on the flap 307. The combined effect is shown in the right-hand portion of the schematic representation. Added together, these forces and moments are the forces and moments that the support member 302 and the azimuth and elevation drive mechanism must work against to maintain the solar energy substrate 304 at an angle α relative to a horizontal plane (i.e., at the desired orientation). The sum of the moments can be calculated as shown below:

ΣM= ⁻ M _(y)+⁻ M _(y2) −F _(z2) X ₂ +F _(x2) Z ₂

Extending the length L of the flap 307 causes the forces in X to change, usually increasing, and the force F_(x2) can increase to a considerable size. This force F_(x2) adds more force on the support member 302 in the x-direction. At a distance x2 from the support member 302, the force F_(x2) also causes a positive rotational moment that counters the large M_(y) moment induced on the solar energy substrate 304. However, generally, the cost of resisting forces F is less than the cost of resisting rotational moments. That is, because static structures such as poles or extruded steel, which may be used to form the support member 302, are cheaper than gears, motors, actuators and other such drive mechanisms, it is less expensive to build a sturdier support member 302 than to resist a rotational moment with a drive mechanism. When the angle Θ is negative and the flap 307 is folded down against the solar energy substrate 304, the overall aerodynamics are substantially the same as if the flap 307 was not present in the solar energy system 300.

The flap 307 is dimensioned and positioned so that the forces and moments present on the solar energy system 300, when summed together, present a zero or near-zero rotational moment on the solar energy substrate 304. Because the wind load 316 is not constant, the position of the flap 307 can be dynamically adjusted in accordance with the dynamic wind load 316 to maintain the rotational moment as close to zero as possible. The actuator mechanism 303, which in this example is a linear actuator, can be extended to push the flap up and increase the angle Θ or retracted to pull the flap down and decrease the angle Θ, although other forms of actuator can be used. Other non-limiting examples of actuator mechanisms include a spring or flexible material at the hinge point, a motor and a linkage mechanism.

FIGS. 3 and 4 illustrate an example where the wind 316 is directed substantially at the front face of the solar energy substrate 304. However, it should be understood that the wind can be incident on the solar energy substrate 304 from other directions and from more than one direction at once, and may be due to gusting and/or vortices. Accordingly, it should be understood that although the example forces and moments shown in FIG. 4 relate to wind coming from the direction of the wind 316 shown, that when the wind is coming from other directions, different forces and moments can be produced on the solar energy substrate 304, and the overall value calculated in a similar manner as shown.

The example shown in FIGS. 3 and 4 has the flap assembly 305 coupled to the upper edge region of the solar energy substrate 304. It should also be understood that if the flap assembly is coupled to the lower edge or to a side edge, the effect on the forces and moments on the solar energy substrate 304 is different than that shown for the particular case where the flap is attached to the upper edge region. As such, the overall value of the forces and moments acting on the solar energy substrate will be different for differently positioned flap assemblies, but can be calculated in a similar manner as shown.

In some implementations, the actuator mechanism 303 is absent, and the flap self-aligns in the wind. Although in these implementations the position of the flap 307 is not controlled, the presence of the flap 307 can move trailing eddies such that the drag and moments on the solar energy substrate 304 are improved.

FIG. 5 is a schematic representation of an example solar energy system 500 including two flap assemblies 505 a, 505 b. In the example solar energy system 500 shown, the two flap assemblies 505 a, 505 b are coupled to an upper edge of the solar energy substrate 504. However, in other implementations, there can be more or fewer flap assemblies and they can be coupled to more, fewer and/or different edges of the solar energy substrate, as is discussed further below in reference to FIG. 6.

A rear perspective view of the solar energy system 500 is shown, so that the components of the flap assemblies are visible. Each flap assembly 505 a, 505 b includes a flap 507 a, 507 b that is coupled to the upper edge region of the solar energy substrate 504 with a hinged connector 509 a, 509 b, providing relative pivotal movement of the flaps 507 a, 507 b about the hinge point. Each flap assembly includes an actuator mechanism 503 a, 503 b, which in this example is a linear actuator that can extend or retract to change the angle of the flap.

The solar energy substrate 504 is mounted to a support member 502 with a rack assembly 508 and is rotatable about the x-axis and the z-axis (per the coordinate system 501), such that the elevation and azimuth respectively of the solar energy substrate 504 can be adjusted. A drive mechanism 506 is configured to move the solar energy substrate 504 to adjust the azimuth and the elevation. The drive mechanism can be, for example, a first motor to adjust the elevation, i.e., pitch, of the substrate and a second motor to adjust the azimuth, i.e., rotation about an axis parallel to a linear axis of the support member 502 (i.e., the z-axis).

A control system 512 can be configured to control the positioning of the solar energy substrate 304, e.g., based on the position of the solar energy substrate relative to the Sun. In the example shown, the control system 512 is shown as a control system positioned locally at the solar energy system 500 and coupled to the drive mechanism 506 such that control signals to adjust the azimuth and elevation can be transmitted from the controller to the drive mechanism. It should be understood, that in other implementations, the control system can be implemented remote from the heliostats and can provide signals to the drive mechanism 506, e.g., over a wired or wireless communication network or otherwise. In other implementations, the control system is implemented partially locally and partially remotely.

Whether the control system 512 is local, remote or both, the control system 512 is further configured to transmit signals to the actuator mechanisms 503 a, 503 b to adjust the angle of the flaps 507 a, 507 b. In some implementations, where the drive mechanism 506 is implemented as one or more motors, if the wind load 516 is inducing a moment on the solar energy substrate 504, the one or more motors operate to counter the moment. Accordingly, voltage and current flow through the one or more motors, in excess of what would be present to adjust the orientation of the solar energy substrate 504 for purposes of tracking the Sun. Ideally, the flap assemblies are configured to counter the moment and reduce the excess voltage and current to as close to zero as possible. One or more sensors can be employed to sense the excess voltage and/or current and therefore sense when a wind-induced moment is acting on the solar energy substrate 304. The sensors can provide the sensed information to the control system 512. Based on the sensed information, the control system can signal the actuator mechanism 503 a, 503 b to adjust the angles of the flaps 507 a, 507 b, until the excess voltage and/or current sensed is at a predetermined threshold level (e.g., zero or near-zero). The two flaps 507 a and 507 b can be adjusted to have the same angled positions or different angled positions. In other implementations, a single actuator mechanism can be used to adjust the position of both flaps 507, 507 b at the same time, in which implementations the two flaps always have the same angled position.

In another implementation, where the drive mechanism 506 employs cables to adjust the azimuth and elevation of the solar energy substrate 504, tension in one or more cables can be sensed by one or more sensors. If the tension is near zero, then the rotating moment is near zero. Accordingly, the angular position of the flaps 507 a, 507 b can be adjusted until the sensors detect that the tension is near zero. Other configurations of drive mechanisms and sensors can be used, and the ones described above are non-limiting examples for illustrative purposes.

In some implementations, the one or more flap assemblies 507 a, 507 b can be operated to purposely move the solar energy substrate 504 into a position. For example, a “stow position” can refer to a position where the solar energy substrate 504 is stowed when not in use (i.e., when not tracking the sun or reflecting solar rays toward a receiver). In one example, the stow position is parallel to the ground. This position could be employed to protect the solar energy substrate 504 against unusually high winds. If it is desired to stow the solar energy substrate 504 in a position parallel to the ground, while the wind load 516 approaches the mirrored face of the substrate 504, then the flaps 507 a,b can be deployed upward. This can increase the wind bearing portion of the system above the hinge point 510, which in turn can increase the rotational moment, M_(y), about the hinge point 510. The added moment can assist the actuators in orientating the substrate 504 in the parallel position.

In another example, the stow position is substantially perpendicular to the ground. In this example, the actuators 503 a,b can shorten and pull down the flaps 507 a,b. This can more nearly balance the wind bearing area of the substrate 504 around the hinge point 510, such that the wind moment, M_(y), can be minimized. To achieve the same perpendicular stow position if the flap assemblies 505 a,b are attached to the bottom edge of the substrate (rather than the top edge as shown), the flaps 507 a,b can be deployed outward to increase the wind bearing area below the hinge point 510.

In some implementations, if the actuator mechanisms 503 a, 503 b lose communication with the control system 512, then as a fail-safe, and if wind is present, the flap assemblies can be deployed to move the solar energy substrate 504 into a stow position. Other scenarios are possible. The flap assemblies 507 a, 507 b can be positioned, in conjunction with a current wind load, so as to facilitate movement of the solar energy substrate 504 into the stow position.

In other implementations, where the solar energy substrate 504 is a reflective surface configured to reflect solar rays to a receiver, the flap assemblies 507 a, 507 b can be employed to quickly move the solar energy substrate 504 into a position so that light reflected toward the receiver is defocused or spills over the receiver surface. For example, during points of a day of high solar intensity, to protect the receiver surface, one or more heliostats in a heliostat field may be purposely moved off-target. The flap assemblies can be used, if there is wind present, to facilitate this movement of the solar energy substrate 504.

In the example solar energy system 500 shown, the solar energy substrate 504 is mounted approximately at its center of gravity. However, it should be understood that in other implementations the solar energy substrate 504 is mounted off its center of gravity. For example, the solar energy substrate 504 can be mounted such that it always wants to rotate downward or alternatively so that it always wants to rotate upward. One or more flap assemblies can still be used in such a system. The mathematics to determine the forces and moments acting on the solar energy substrate 504 and flaps 505 a, 505 b is adjusted accordingly. However, similarly as discussed above, the flaps can still be used to help reduce the moment acting on the solar energy substrate on account of wind, and to use the wind together with the flaps to help move the solar energy substrate, e.g., into a stow position.

In some implementations, a locking mechanism can be included in each flap assembly 505 a,b, which mechanism is configured to freeze the position of the corresponding actuator 503 a,b (or flaps 507 a,b directly) to hold the corresponding flaps 507 a,b in their positions. For example, if the actuator 503 a positions the flap 507 a and the holding torque or force has to continually consume energy to maintain the position, by employing the locking mechanism to effectively lock the flap 507 a in the position, less energy can be consumed. Some non-limiting examples of locking mechanisms include mechanical pins, grips and clutches.

It should also be understood that the solar energy systems 300 and 500 shown in FIGS. 3 and 5 respectively are simplified schematic representations. Other forms of solar energy systems can be used. For example, the shape of the solar energy substrates can be curved rather than flat and can be a unitary surface or multiple surfaces (e.g., faceted). Different configurations of support member can be used. Different mounting mechanisms to mount the solar energy substrate to the support member can be used. Differently configured and positioned drive mechanisms can be used.

FIG. 6 is a schematic representation of a front view of an example solar energy system 602 with multiple flap assemblies. A single solar energy substrate 602 is shown with all of these flap assemblies to illustrate some of the different configurations and placements of flaps, and in practice one solar energy substrate 602 would more typically employ fewer flaps than shown.

In some implementations, a single flap assembly is coupled to an edge region of the solar energy substrate. For example, the solar energy system 600 includes a single flap assembly having a single flap 606 coupled to the upper edge of the solar energy substrate 602. In some implementations, two or more flap assemblies are coupled to an edge region of the solar energy substrate. For example, the solar energy system 600 includes two flap assemblies having flaps 612 a and 612 b coupled to the lower edge of the solar energy substrate. The flaps 612 a and 612 b could be implemented alone or together with flaps on other edges of the solar energy substrate. As another example, the solar energy system 600 includes three flap assemblies having flaps 610 a, 610 b and 610 c coupled to the left edge of the solar energy substrate 602. For illustrative purposes, these flaps are shown with a different shape as compared to the other flaps shown in the figure. That is, the flaps 610 a-c are coupled to the solar energy substrate with hinged connections along their width rather than their length, as is the case with the other flaps shown.

In some implementations, flap assemblies can be coupled to one or both side edges of the solar energy substrate, for example, to reduce a twisting moment acting on the solar energy substrate. For example, the three flaps 610 a-c are shown coupled to the left side edge of the solar energy substrate 604 and the one long flap 608 is shown coupled to the right side edge of the solar energy substrate 604.

As mentioned above, the various flap positions and sizes shown in FIG. 6 are to illustrate a few examples of configurations of flap assemblies. That is, there can be one or more coupled to a single edge region of the solar energy substrate 602. There can be one or more coupled to two or more edge regions. The flaps can be coupled to the edge region of the solar energy substrate along their width or their length. The flaps coupled to a particular edge region can be independently movable relative to each other or else coupled together so as to be moved together as a unit.

Although the flap assemblies described above are coupled to an edge of the solar energy substrate, it should be understood that the flap assemblies can be coupled differently to the solar energy substrate. That is, the description herein to an ‘edge’ can include the ‘edge region’ of the solar energy substrate, which can include part of the front and/or rear face of the substrate. For example, a flap assembly can be coupled to the front face or the rear face of the solar energy substrate 602, rather than directly on the edge, i.e., the flap assembly can be coupled to an ‘edge region’. Additionally, as previously mentioned above, the flap assembly can be connected directly to the solar energy substrate or can be connected to a different part of the system, e.g., a mounting framework for the solar energy substrate, and thereby still coupled (albeit indirectly) to the solar energy substrate.

FIGS. 7A, 7B and 7C are schematic representations of an example solar energy system with a retractable flap assembly. FIG. 7A shows a side view of the simplified solar energy system that includes a solar energy substrate 702 mounted to a support member 704. A retractable flap assembly is mounted to an upper region of the solar energy substrate 702. The flap assembly includes a flap 706 that is slidably moveable in the direction indicated by the arrow 708. In FIG. 7A, the flap is shown extended from the upper edge of the solar energy substrate 702 by length L₁. That is, the effective length of the flap 706 for purposes of affecting the aerodynamics of the solar energy substrate 702 is L₁. In FIG. 7B, the flap 706 is extended further and has an effective length of L₂, which is greater than L₁. In FIG. 7C, the flap has been retracted and extends a lesser amount being a length L₃. In this implementation, the effective length of the flap 706 is variable, however, the angle of the flap 706 relative to the substrate 702 is not variable. That is, the flap 706 is parallel to the substrate 702. In other implementations, the length of the flap can be variable and the angle can be varied. For example, the flap assembly can include an actuator mechanism that permits slidable movement in the direction 708, but also operates to tilt the flap toward the right, such that the angle of the flap 706 can be different than the angle of the substrate 702. In the example shown, the retractable flap assembly is coupled to the upper portion of the solar energy substrate 702. However, in other implementations, the retractable flap assembly can be coupled to a different portion (e.g., the lower portion or a side portion) and more than one retractable flap assembly can be included in the solar energy system, including either more than one coupled to the same portion or different portions or both. In other implementations, the retractable flap assembly includes a flap that pivots (rather than slides) about a point, and can pivot about the point to expose the flap from behind the substrate 702, and can be pivoted back to hide the flap (or part of the flap) behind the substrate 702.

FIG. 8 is a flowchart showing an example process 800 for controlling the orientation of a solar energy substrate. The flap assembly described herein can be used, as discussed, to reduce or eliminate a wind-induced moment acting on a solar energy substrate of a solar energy system. However, generally, a primary concern is that the solar energy substrate is properly orientated to perform most efficiently under current conditions. That is, if the solar energy system is a heliostat and the solar energy substrate is a reflective surface that is operable to receive solar rays and reflect them toward a solar energy collector (e.g., a receiver), then the orientation of the solar energy substrate changes throughout the course of a day so as to track the Sun's current position relative to the solar energy substrate and to the solar energy collector. Similarly, if the solar energy substrate is a photovoltaic panel, then the orientation of the solar energy substrate will also change throughout the course of a day so as to track the Sun's current position. The position of the Sun relative to the solar energy substrate will also vary from day to day throughout the year, which is generally taken into account when determining how to position the solar energy substrate.

As such, the process 800 includes adjusting the orientation of the solar energy substrate based on the position of the Sun (802). A determination can be made whether the solar energy substrate is in alignment with a current desired position of the solar energy substrate, e.g., based on the position of the Sun (804). For example, a control system can operate to determine a desired orientation of the solar energy substrate and an actual orientation of the solar energy substrate and compare the two to determine whether the solar energy substrate is in alignment, although other techniques can be used.

If the solar energy substrate is determined not to be in alignment (“No” branch of 804), then the orientation of the solar energy substrate can be adjusted again (802). If the solar energy substrate is determined to be in alignment (“Yes” branch of 804), then a determination can be made whether a wind-induced moment is detected acting on the solar energy substrate (806).

If a wind-induced moment is detected acting on the solar energy substrate (“Yes” branch of 806), then the position of one or more flaps of one or more flap assemblies coupled to the solar energy substrate can be adjusted (808). Various techniques can be used to detect the presence of a wind-induced moment. For example, as discussed above, if the solar energy substrate is positioned in azimuth and/or elevation by one or more motors, then the one or more motors will be operating to counter the wind so as to maintain the solar energy substrate in the desired orientation. Voltage and/or current present in the one or more motors can be detected and based on the voltage or current, a determination made that the one or more motors are operating to counter a wind-induced moment, and therefore a wind-induced moment is present. In another implementation where cables are used to orientate the substrate, the detection of tension over a predetermined threshold value in one or more cables can be used to determine that the cables are operating against a wind-induced moment to maintain the current orientation of the substrate, and therefore a wind-induced moment is present. Other drive mechanisms and detection techniques can be used.

After the position of the one or more flaps has been adjusted, another determination can be made as to whether a wind-induced moment is detected (806). If the wind-induced moment is still present, then the position of one or more flaps can be adjusted again, which steps can be repeated until the wind-induced moment is reduced to a predetermined threshold level (e.g., zero or near-zero).

If a wind-induced moment is not detected (“No” branch of 806), then a determination can be made as to whether the solar energy substrate is still in alignment (804). If mis-alignment is detected, the orientation of the solar energy substrate can be adjusted, which steps can be repeated until the solar energy substrate is in alignment with a desired position.

In some implementations, adjusting a position of one or more flaps (i.e., step 808) can be triggered by a detection that the solar energy substrate is oscillating. That is, step 806 of detecting a wind-induced moment can also include detecting whether or not the solar energy substrate is oscillating at all or over a predetermined threshold value. For example, as was mentioned above, if the wind-induced moment is reduced to zero, the substrate can end up oscillating. If oscillation is detected, then the position of one or more flaps can be adjusted to dampen the oscillations.

Process 800 illustrates that the primary consideration is keeping the orientation of the solar energy substrate on target, and that secondary considerations can be reducing or eliminating any wind-induced moment acting on the substrate and/or oscillations of the substrate. In other implementations, the priorities of these considerations can be different.

As discussed above, the flap included in a flap assembly can extend the length of an edge of the solar energy substrate or can have a shorter length than the edge. The flaps shown have rectangular shapes and are generally planar. The flaps can be formed from various materials that are durable, for example, sheet metal or plastic. In other implementations, the flap can have a different shape than rectangular. For example, the flap have a substantially triangular shape and be connected to the solar energy substrate at a corner of the flap. In some implementations, the edge of the flap can be modified to include one or more features, e.g., comb features, teeth or holes, to aerodynamically alter the way wind sheds off the flap's edge, which may help to steady the flap. Other configurations are possible.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.

In addition, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other embodiments are within the scope of the following claims. 

1. A solar energy system comprising: a solar energy substrate mounted on a support member and configured to receive solar rays from the Sun and configured to move in at least one direction such that an orientation of the solar energy substrate can be adjusted in accordance with a direction of the solar rays; the support member configured to support the solar energy substrate; and one or more flap assemblies coupled to the solar energy substrate, wherein each flap assembly includes a flap and an actuator that is configured to move the flap relative to the solar energy substrate and movement of the flap is controllable to counter a wind-induced moment acting on the solar energy substrate.
 2. The solar energy system of claim 1, further comprising: a control system configured to: receive information that indicates the wind-induced moment is acting on the solar energy substrate; and control movement of the one or more flaps to reduce the wind-induced moment.
 3. The solar energy system of claim 1, wherein the solar energy substrate comprises a heliostat mirror configured to reflect the received solar rays toward a solar energy collector.
 4. The solar energy system of claim 1, wherein the solar energy substrate comprises a photovoltaic panel.
 5. The solar energy system of claim 1, wherein the solar energy substrate comprises a unitary member.
 6. The solar energy system of claim 1, wherein the solar energy substrate comprises two or more members.
 7. The solar energy system of claim 6, wherein orientations of the two or more members are independently adjustable.
 8. The solar energy system of claim 1, wherein the one or more flaps of the one or more flap assemblies are connected to one or more edge regions of the solar energy substrate.
 9. The solar energy system of claim 1, wherein: each flap of the one or more flap assemblies is connected to an edge region of the solar energy substrate and is positioned at an angle relative to a first plane that is different than an angle of the solar energy member relative to the first plane; and the angle of the flap relative to the first plane is determined based on a strength of the wind-induced moment acting on the solar energy substrate.
 10. The solar energy system of claim 9, wherein: each flap is connected to the edge region with a hinge that provides pivotal movement of the flap relative to the solar energy substrate; and each actuator of the one or more flap assemblies comprises a linear actuator coupled at a first end to the solar energy member and at a second end to the flap and is configured to change the angle of the flap relative to the first plane.
 11. A method comprising: (a) detecting that a wind-induced moment is acting on a solar energy substrate mounted to a support structure, wherein the solar energy substrate is positioned at a particular time in a desired position relative to a position of the Sun at the particular time and in the desired position the solar energy substrate is at an angle α relative to a first plane; (b) in response to detecting the wind-induced moment, adjusting a position of a flap coupled to an edge region of the solar energy substrate including adjusting an angle Θ of the flap relative to the first plane, wherein the angle Θ is different than the angle α; and (c) repeating steps (a) and (b) until the detected wind-induced moment is reduced to a strength that is less than or equal to a predetermined threshold value.
 12. The method of claim 11, wherein detecting that a wind-induced moment is acting on the solar energy substrate comprises detecting at least one of voltage or current in one or more motors configured to adjust a position of the solar energy substrate and operating at the particular time to counter the wind-induced moment and maintain the solar energy substrate in the desired position.
 13. The method of claim 11, wherein detecting that a wind-induced moment is acting on the solar energy substrate comprises detecting tension exceeding a threshold value in one or more cables configured to adjust a position of the solar energy substrate and operating at the particular time to counter the wind-induced moment and maintain the solar energy substrate in the desired position.
 14. The method of claim 11, wherein adjusting the position of the flap comprises operating a linear actuator to extend or retract a linear member that is coupled to the flap at a first end and to the solar energy substrate at a second end to adjust the angle Θ of the flap relative to the first plane.
 15. A solar energy system comprising: a solar energy substrate mounted on a support member and configured to receive solar rays from the Sun and configured to move in at least one direction such that an orientation of the solar energy substrate can be adjusted in accordance with a direction of the solar rays; the support member configured to support the solar energy substrate; and one or more flap assemblies coupled to the solar energy substrate, wherein each flap assembly includes a flap and an actuator that is configured to move the flap relative to the solar energy substrate and movement of the flap is controllable to control movement of the solar energy substrate.
 16. The solar energy system of claim 15, further comprising: a control system configured to: receive information that indicates that the solar energy substrate is oscillating; and control movement of the one or more flaps to reduce oscillation of the solar energy substrate.
 17. The solar energy system of claim 15, further comprising: a control system configured to: receive information that indicates that a wind-induced moment is acting on the solar energy substrate; and control movement of the one or more flaps to reduce the wind-induced moment.
 18. The solar energy system of claim 15, further comprising: a control system configured to: receive information that indicates that a wind load is acting on the solar energy substrate; and control movement of the one or more flaps to adjust a position of the solar energy substrate using the wind load. 